The invention relates to surgical instruments. More particularly, the invention relates to a needle assembly particularly suited for bone marrow aspiration and intraosseous infusion.
Known biopsy needles generally include a cannula having a lumen extending therethrough, and a trocar or stylet which is removably inserted through the lumen of the cannula. The proximal ends of the cannula and trocar are provided with some type of gripping means and the distal ends of the cannula and trocar are sharpened to a bone piercing edge. In order to aspirate bone marrow or infuse into the bone, the trocar and cannula are forced through the outer hard layer of the bone containing the marrow. Once the softer, internal region of the bone is reached, the trocar is withdrawn and a through-passage to the internal region of the bone is defined by the lumen extending through the cannula.
Early problems with biopsy needles involved the sharpness of the cannula and trocar and the gripping means used so that the needle could be placed accurately and the bone could be penetrated quickly. U.S. Pat. No. 4,356,828, for example, discloses an improved finger gripping member and U.S. Pat. No. 4,403,617 discloses particular cutting edge configurations for the trocar and cannula.
Developments in the gripping means of the trocar and cannula continued with emphasis placed on the secure engagement of the trocar within the cannula and ease of use for the physician. U.S. Pat. Nos. 4,922,602; 4,838,282, 4,793,363 and 4,469,109 for example, disclose fairly elaborate interlocking systems between the trocar gripping means and the cannula gripping means and different shapes for the gripping means.
While some of these biopsy needles are often used for extracting a core sample of bone marrow, most of the biopsy needles are used for aspiration by connecting an aspirating syringe to the proximal end of the cannula and aspirating marrow fluid through the cannula into the syringe. Moreover, these types of needles are sometimes used in pediatrics where an intravenous infusion is difficult because of the small size of an infant's veins. In these applications, an IV bag or the like is attached to the proximal end of the cannula via a fluid conduit and IV fluids are infused directly into bone marrow through the cannula.
In both the aspiration and infusion applications, it is advantageous to provide a fluid connection at the proximal end of the cannula. Moreover, when inserting such a needle into the sternum, it is important to regulate the depth of penetration so that the needle does not protrude through the sternum and into the aorta.
U.S. Pat. No. 4,469,109 to Mehl addresses many of these concerns by providing a bone marrow biopsy needle having a cannula and a cannula housing supporting the cannula. The proximal end of the cannula housing is provided with an angled chamber having a luer taper for receiving a syringe adapter and the distal end of the housing includes a partially threaded portion which engages a threaded depth stop having a flared bottom. By rotating the depth stop relative to the cannula, the piercing length of the cannula is effectively limited. A stylet having a stylet cap supporting the stylet is insertable into the cannula and is lockable in position by interaction of a locking groove in the stylet cap and an outward projection in the cannula housing. The cannula housing is provided with vertical wings extending outward from the housing for gripping by the physician.
Mehl's biopsy needle is an improvement over many of the preceding devices but still presents several problems. Rotation of the threaded depth stop relative to the cannula housing is limited only by whatever frictional resistance may or may not exist between the threads. This can be a substantial disadvantage where the penetration depth of the cannula must be precisely limited. In Mehl's needle assembly, the depth stop could easily rotate out of the desired position causing an unwanted change in the effective piercing length of the cannula. Moreover, the tapered chamber in the proximal end of Mehl's cannula housing provides only a minimal connection for a fluid conduit. This can be a substantial disadvantage when coupling a fluid source to the cannula for a long-term infusion. In particular, the simple luer taper may not be sufficient to securely couple with a fluid conduit from an IV bag or the like. In addition, Mehl's vertical wings, which provide cannula gripping means, are uncomfortable to the physician. This is substantial disadvantage in all bone marrow procedures since the insertion of these needles through bone requires significant effort by the physician.